1. Field of the Invention
The invention is directed to a method for controlling the thickness of walls during casting. In particular, the method controls the wall thickness for a turbine, for example an internally cooled turbine of the bucket and nozzle type.
2. Description of Related Art
Current casting methods for large power generation engine buckets and nozzles do not result in a wall with a sufficient thickness with acceptable tolerances. In one known method for casting engine buckets and nozzles, a core is supported inside a mold, for example by a set of core locator devices. Each core device can comprise an indentation on the core and a protrusion on the mold. The indention and protrusion are at positions that correspond to each other. However, this type of core locator device does not provide a sufficient wall thickness, with acceptable tolerances, to satisfy the demands made on power generation engine buckets and nozzles, particularly large power generation engine buckets and nozzles.
In a further method for casting of relatively small turbine structures, such as those in small aircraft engines, a core is typically set inside a mold by a series of pins, for example constructed at least in part of platinum. However, even according to this method, the platinum pins do not provide a sufficient strength to support large cores in the casting of large power generation engine buckets and nozzles.